This and a companion project (Z01 HD001123) investigate auditory communication in primates. The overall goal of these studies is to provide a comprehensive understanding of primate auditory communication in terms of development, neural mechanisms, endocrine factors, and social context. Two species, the squirrel monkey and the common marmoset, are the main subjects of study, with additional data collected from other species where appropriate. The present project studies primate communication from a bioacoustic and ethological perspective, focusing on the detailed acoustic structure of vocalizations produced in natural settings, and the relationship of structural differences to differences in age, gender, experience and response selectivity, as well as the broader factors of social context and genetic background. New findings this year: In a new initiative to determine the genetic factors underlying expression of a range of behaviors in the common marmoset, infant cries have been analyzed in detail to identify acoustic markers that are shared by sibs, family members or other genetically related individuals. A Summer IRTA Fellow, Karen Ladd, used ?Raven? (a software program developed at Cornell University?s Bioacoustics Program) to measure specific points on sonagraphic displays of infant cries, then wrote a macro in Microsoft Excel that calculated 19 parameters from these measures. A total of 1646 cries from 41 infants were measured. A high degree of individuality came out of the analysis. This means that there were sufficient differences in the acoustic structure of the cries of each infant to mask possible familial similarities. Further analysis indicated that this high degree of individuality is found when all of the vocalizations from a particular individual are included in the analysis, but largely disappears when a smaller subset of calls are used. With a smaller subset, it is possible to show a strong resemblance in the calls of infants from a given parentage. Future work will compare the calls of parents and those of infants, to test for inter-generational transmission of familial vocal traits.